Method and device for embedding watermark information into real-time track data

Abstract

The invention relates to the technical field of geographic information security, in particular to a method and device for embedding watermark information into real-time track data. The method comprises the following steps: splitting track data obtained in real time according to a preset data extraction mode to obtain at least one sub-track segment; according to the space attributes and the time attributes of the sub-track segments, the space-time track data corresponding to the sub-track segments are converted to obtain time-frequency matrix data, and the time-frequency matrix data comprise a plurality of frequency values; determining at least one frequency peak value from the frequency values corresponding to the sub-track segments; determining a timestamp corresponding to the frequency peak value according to a corresponding relation between the frequency peak value and a time index, and calculating a watermark index of the timestamp; performing parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index; and performing inverse short-time Fourier transform by using the frequency value after the parity operation and the original phase of the frequency value to obtain track data embedded with watermark information.

Description

Technical Field

[0001] The implementation of the present invention relates to the technical field of geographic information security, and particularly relates to a method and device for embedding watermark information into real-time trajectory data. Background Art

[0002] With the rapid development of Internet technology and mobile terminal positioning technology, more and more location-based service applications have entered people's lives. The trajectory data of users is mostly stored, analyzed, published, and mined in the form of trajectory sequences supplemented by location information. It is widely used in fields such as urban planning, transportation, and behavior analysis, and has played a huge role in modern people's life production, scientific research, and enterprise development. However, since trajectory data contains a large amount of user privacy information, it is extremely easy to be stolen during the process of transmission and sharing, and the resulting copyright protection issues have seriously hindered the application and research of trajectory data.

[0003] Existing classic digital watermarking technologies are all for offline trajectory data, that is, after the data is collected and then uniformly processed, watermark information is embedded. However, such algorithms cannot provide security protection during the process of trajectory data collection and upload, and data theft is extremely likely to occur during this process. Therefore, it is urgent to study security protection algorithms for real-time trajectory data to achieve copyright protection during the process of collecting original trajectory data.

[0004] Although rich achievements have been made in the research of existing geographic data digital watermarking algorithms, currently, there is no algorithm that applies digital watermarking to real-time trajectory data, and it is impossible to achieve the security effect of protecting the data from being damaged throughout the process. Summary of the Invention

[0005] The embodiments of the present invention provide a method for embedding watermark information into real-time trajectory data, which can be used to solve related problems in the prior art. The method specifically includes: According to a preset data extraction method, the real-time obtained trajectory data is split to obtain at least one sub-trajectory segment; According to the spatial attribute and time attribute of the sub-trajectory segment, the spatio-temporal trajectory data corresponding to the sub-trajectory segment is transformed into time-frequency matrix data, and the time-frequency matrix data includes multiple frequency values; At least one frequency peak is determined from the frequency values corresponding to the sub-trajectory segment; According to the correspondence between the frequency peak and the time index, the time stamp corresponding to the frequency peak is determined, and the watermark index of the time stamp is calculated; Based on the value of the watermark information corresponding to the watermark index, a parity operation is performed on the frequency value corresponding to the watermark index; Performing an inverse short-time Fourier transform on the frequency value after completing the parity operation and the original phase of the frequency value to obtain the trajectory data embedded with watermark information.

[0006] Specifically, determining at least one frequency peak from the frequency values corresponding to the sub-trajectory segments includes: Calculating the amplitude spectrum of each data in the time-frequency matrix data; Taking the frequency values within a preset range of the amplitude spectrum as the frequency peaks.

[0007] Further, before determining the time stamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index and calculating the watermark index of the time stamp, it further includes: Generating a random sequence using a two-dimensional mapping method, performing an exclusive OR operation on the random sequence and the image binary sequence to complete the encryption operation of the obtained copyright information.

[0008] Specifically, performing a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index includes: When the value of the watermark information corresponding to the watermark index is 0, adjusting the frequency value corresponding to the watermark index to an even number; When the value of the watermark information corresponding to the watermark index is 1, adjusting the frequency value corresponding to the watermark index to an odd number.

[0009] Specifically, splitting the real-time obtained trajectory data into at least one sub-trajectory segment according to a preset data extraction method includes: Making the data at the first preset position in the currently split sub-trajectory segment coincide with part of the data in the previous sub-trajectory segment; Making the data at the second preset position in the currently split sub-trajectory segment coincide with part of the data in the subsequent sub-trajectory segment; The first preset position is before the second preset position.

[0010] Specifically, calculating the watermark index of the time stamp includes: Calculating the watermark index for the time stamp using a hash function, and the formula is as follows:

[0011] is the time index, is the hash value of the time index, is the watermark index calculated according to the time index.

[0012] An embodiment of the present invention provides a device for embedding watermark information in real-time trajectory data, and the device includes: A splitting module, configured to split the real-time acquired trajectory data according to a preset data extraction method to obtain at least one sub-trajectory segment; A conversion module, configured to convert the spatio-temporal trajectory data corresponding to the sub-trajectory segment into time-frequency matrix data according to the spatial attribute and time attribute of the sub-trajectory segment, where the time-frequency matrix data includes multiple frequency values; A first determination module, configured to determine at least one frequency peak from the frequency values corresponding to the sub-trajectory segment; A second determination module, configured to determine a time stamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index, and calculate the watermark index of the time stamp; An operation module, configured to perform a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index; A transformation module, configured to perform an inverse short-time Fourier transform on the frequency value after the parity operation and its original phase to obtain the trajectory data embedded with the watermark information.

[0013] Specifically, the first determination module is specifically configured to: Calculate the amplitude spectrum of each data in the time-frequency matrix data; Use the frequency values within a preset range of the amplitude spectrum as the frequency peaks.

[0014] Furthermore, the apparatus further includes: An encryption module, configured to generate a random sequence using a two-dimensional mapping method, and perform an exclusive OR operation on the random sequence and the image binary sequence to complete the encryption operation on the acquired copyright information.

[0015] An embodiment of the present invention further provides an electronic device, characterized in that the electronic device includes a processor, a memory, and a program or instruction stored on the memory and executable on the processor, and the program or instruction is executed by the processor to perform the steps of a method for embedding watermark information in real-time trajectory data.

[0016] Using the method provided by the embodiment of the present invention, for the possible problems of illegal theft and copyright confirmation during the real-time acquisition, transmission, and shared use of trajectory data, as well as the real-time acquisition and transmission requirements of data, copyright information can be embedded in real-time during the data acquisition process, and blind detection and extraction of watermark information can be achieved. The proposed algorithm has high robustness. Description of the Drawings

[0017] Figure 1 is a flowchart of a method for embedding watermark information in real-time trajectory data provided by an embodiment of the present invention; Figure 2Schematic structural diagram of a device for embedding watermark information into real-time trajectory data provided by an embodiment of the present invention. Detailed implementation manners

[0018] To make the above objects, features, and advantages of the present application more apparent and understandable, the following will describe the detailed implementation manners of the present application in conjunction with the accompanying drawings. Many specific details are set forth in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0019] In the description of the present application, it should be understood that if there are terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., the orientation or positional relationship indicated by these terms is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application.

[0020] In addition, if there are terms such as "first" and "second", these terms are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, if there is a term "plurality", the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0021] Trajectory data is a time-series data composed of discrete points, which not only has spatial geometric attributes but also has time attributes, and is also a type of geospatial big data. Therefore, the digital watermarking algorithm for vector geospatial data can provide a reference for the digital watermarking algorithm for trajectory data. Existing digital watermarking algorithms for vector geospatial data can be divided into three categories according to the embedding domain: geometric domain, frequency domain, and attribute information. Among them, the geometric domain is mostly for line and surface data, and for trajectory data, due to its unique operations (such as trajectory data cleaning, etc.), geometric features are easily lost, and the robustness of such algorithms applied to trajectory data is poor; while the attribute information of trajectory data generally involves user privacy information, so it is also not advisable to embed copyright information using attribute information; and the frequency domain algorithm, due to its high concealment and strong robustness, can be effectively applied to trajectory data. To solve these problems, the relevant methods of the embodiments of the present invention are proposed.

[0022] An embodiment of the present invention provides a method for embedding watermark information into real-time trajectory data, as Figure 1 shown, the specific process is as follows: Step 11: According to a preset data extraction method, split the real-time acquired trajectory data to obtain at least one sub-trajectory segment; the specific process in this step is as follows: In this step, it is required that the data at the first preset position in the currently split sub-trajectory segment coincides with part of the data in the previous sub-trajectory segment; Make the data at the second preset position in the currently split sub-trajectory segment coincide with part of the data in the subsequent sub-trajectory segment; The first preset position is before the second preset position. That is, the data in the front part of the current sub-trajectory segment should overlap with the data in the back part of the previous sub-trajectory segment; the data in the back part of the current sub-trajectory segment should overlap with the data in the front part of the subsequent sub-trajectory segment.

[0023] The specific explanation for this step is as follows: The trajectory data to be collected by this method can be any trajectory data, such as GPS data, sensor data, lidar data, etc.

[0024] First, segment the trajectory data according to a preset data extraction method. The preset data extraction method can be to segment the real-time trajectory data according to the set time threshold. For example, the trajectory data is often collected at a sampling interval of 0.1 second or 50 milliseconds. Therefore, this method uses a 5-second time threshold to segment the real-time trajectory data to generate sub-trajectories . Among them, represents the th sub-trajectory segment, is the total number of sub-trajectory segments. That is, whenever 5 seconds of data is collected, this segment of data is decomposed into a sub-trajectory segment, and subsequent processing is performed on this sub-trajectory segment.

[0025] At the same time, in order to resist the time attack of trajectory data, the overlapping window method is used for segmentation to ensure that each window contains the time information of the front and back parts and enhance the time continuity.

[0026] Step 12: According to the spatial and temporal attributes of the sub-trajectory segment, convert the spatio-temporal trajectory data corresponding to the sub-trajectory segment into time-frequency matrix data, and the time-frequency matrix data includes multiple frequency values; this step specifically includes: Perform time-frequency analysis on each sub-trajectory segment data, that is, use the Short Time Fourier Transform (STFT) to convert the spatio-temporal trajectory data into a time-frequency matrix data, where is the frequency value, is the time, and the STFT conversion formula is as shown in formula (1): Formula (1)

[0027] Select an appropriate window function to process the real-time spectrum signal. In this method, a Hamming window is used to control spectrum leakage.

[0028] Step 13: Determine at least one frequency peak from the frequency values corresponding to the sub-trajectory segments. This step specifically includes: Calculate the amplitude spectrum of each data in the time-frequency matrix data; use the frequency values within a preset range of the amplitude spectrum as the frequency peaks. For example: First, perform feature extraction on the sub-trajectory segment and calculate the amplitude spectrum of the STFT result of the sub-trajectory segment , where the absolute value is used here to remove the phase information and only focus on the energy distribution of the signal, making the subsequent processing more simplified and facilitating the embedding of watermark information into the amplitude without interfering with the phase.

[0029] For non-stationary signals such as trajectory data (i.e., signals whose features change over time), different time periods may have different frequency components. This will result in multiple frequency peaks in the spectrum of the same time window. Therefore, dynamic frequency range selection is required. Since this method is for real-time trajectory data, an adaptive algorithm needs to be used to dynamically select the frequency range in each segment of the signal based on real-time data analysis.

[0030] In this solution, peak detection can be applied to identify the high-energy frequencies in the signal. By setting an amplitude threshold, filter out the peaks below a certain energy level and only retain the main peaks. Record the qualified peaks and their corresponding frequencies to form a frequency list , and this frequency list includes at least one frequency peak , where 1 ≤ i ≤ n.

[0031] Step 14: Determine the time stamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index, and calculate the watermark index of this time stamp. This step specifically includes: For each peak , identify the specific time index corresponding to this peak in the spectrum , record the corresponding time stamp, and calculate the watermark index for this time stamp using a hash function . The calculation formula is formula (2): Formula (2) where, is the time index, is the hash function, The hash value for this time index is the watermark index calculated according to the time index.

[0032] Step 15: Based on the value of the watermark information corresponding to the watermark index, determine the parity operation for the frequency value corresponding to the watermark index. The specific process of this step is as follows: When the value of the watermark information corresponding to the watermark index is 0, adjust the frequency value corresponding to the watermark index to an even number; when the value of the watermark information corresponding to the watermark index is 1, adjust the frequency value corresponding to the watermark index to an odd number. For example: View the corresponding watermark information, and at the same time check the time index the peak value of the time-frequency matrix data corresponding to . If the watermark information is 0, adjust the peak value of the time-frequency matrix data corresponding to the time index to an even number; if the watermark information is 1, adjust the peak value of the time-frequency matrix data corresponding to the time index to an odd number.

[0033] Step 16: Use the frequency value after the parity operation and the original phase of this frequency value to perform an inverse short-time Fourier transform to obtain the trajectory data embedded with the watermark information. Specifically, it includes: Repeat the above steps until all the frequency values in the frequency list are embedded with the watermark information. Use the adjusted amplitude peak and the original phase to perform an inverse STFT to reconstruct the signal embedded with the watermark, and finally obtain the sub-trajectory segment data embedded with the watermark.

[0034] Repeat the above steps until all the sub-trajectory segments are collected. The obtained trajectory data set is the data set embedded with the watermark information. This process can not only be applied to the trajectory data collected and transmitted in real time, but also be applicable to the trajectory data after offline processing.

[0035] Specifically, before determining the time stamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index and calculating the watermark index of this time stamp, it further includes: Generate a random sequence using a two-dimensional mapping method, and perform an exclusive OR operation on this random sequence and the binary sequence of the image to complete the encryption operation of the obtained copyright information. The specific process is as follows: The copyright information can be any picture, string or other copyright information. In this method, the copyright information is taken as the binary copyright image of, and the image is arranged in rows as a one-dimensional binary sequence .

[0036] Copyright information encryption can use any algorithm. In this method, a two-dimensional Henon map is selected to generate a random sequence, and this random sequence is XOR-operated with the binary sequence of the image to complete the encryption of the copyright information.

[0037] After encryption, the obtained binary ciphertext is the encrypted binary copyright information 。

[0038] Using the method provided by the embodiments of the present invention, for the possible problems of illegal theft and copyright confirmation during the real-time acquisition, transmission, and shared use of trajectory data, as well as the real-time acquisition and transmission requirements of data, copyright information can be embedded in real time during the data acquisition process, and blind detection and extraction of watermark information can be achieved. The proposed algorithm has high robustness.

[0039] In the embodiments of the present invention, the method of using time threshold overlapping windows segments the trajectory data during the data acquisition process, uses the short-time Fourier transform to convert the segmented trajectory data into the frequency domain, extracts the peak list and its corresponding time index in the spectrum according to the spectrum distribution, performs a hash transformation on the time index to generate a watermark index, and finally embeds the watermark information into the peaks through parity quantization.

[0040] This method fully considers the characteristics during the trajectory data acquisition process, combines the characteristics of the trajectory data itself, and effectively ensures the concealment of watermark information embedding by using the method of overlapping window segmentation combined with the short-time Fourier transform. At the same time, this method enables the real-time embedding of copyright information during the real-time acquisition process of trajectory data, and the multi-spectrum repeated embedding not only realizes a large-capacity watermark algorithm but also ensures the robustness against common attacks.

[0041] As Figure 2 shown, the embodiments of the present invention provide a device for embedding watermark information into real-time trajectory data. The device includes: A splitting module 21, configured to split the trajectory data obtained in real time according to a preset data extraction method to obtain at least one sub-trajectory segment; A conversion module 22, configured to convert the spatio-temporal trajectory data corresponding to the sub-trajectory segment into time-frequency matrix data according to the spatial attribute and time attribute of the sub-trajectory segment, where the time-frequency matrix data includes multiple frequency values; A first determination module 23, configured to determine at least one frequency peak from the frequency values corresponding to the sub-trajectory segment; A second determination module 24, configured to determine the time stamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index, and calculate the watermark index of the time stamp; An operation module 25, configured to perform a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index; The transformation module 26 is configured to perform an inverse short-time Fourier transform using the frequency value after the parity operation is completed and the original phase of the frequency value to obtain the trajectory data embedded with the watermark information.

[0042] The first determination module 23 is specifically configured to: Calculate the amplitude spectrum of each data in the time-frequency matrix data; Use the frequency values within a preset range of the amplitude spectrum as the frequency peaks.

[0043] The apparatus further includes: The encryption module 27 is configured to generate a random sequence using a two-dimensional mapping method, perform an exclusive OR operation on the random sequence and the image binary sequence to complete the encryption operation of the obtained copyright information.

[0044] An embodiment of the present invention further provides an electronic device, which is characterized in that the electronic device includes a processor, a memory, and a program or instruction stored on the memory and executable on the processor, and the program or instruction is executed by the processor to perform the steps of any one of the above methods for embedding watermark information in real-time trajectory data.

[0045] In this application, unless otherwise clearly specified and limited, if terms such as "installation", "connection", "connection", "fixation" appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

[0046] In this application, unless otherwise clearly specified and limited, if a first feature is described as "above" or "below" a second feature or the like, its meaning can be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "above", and "on" the second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. The first feature being "below", "below", and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.

[0047] It should be noted that if an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are only for the purpose of illustration and do not represent the only implementation. The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0048] The above-described embodiments merely represent several implementation manners of this application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of the patent of this application shall be subject to the appended claims.

Claims

1. A method for embedding watermark information into real-time trajectory data, characterized in that: The method comprises: According to a preset data extraction method, the trajectory data acquired in real time is split to obtain at least one sub-trajectory segment; According to the spatial attribute and the temporal attribute of the sub-trajectory segment, the spatiotemporal trajectory data corresponding to the sub-trajectory segment is converted into time-frequency matrix data, wherein the time-frequency matrix data includes a plurality of frequency values; Determining at least one frequency peak from the frequency values ​​corresponding to the sub-trace segments; According to the correspondence between the frequency peak and the time index, a timestamp corresponding to the frequency peak is determined, and a watermark index of the timestamp is calculated; Based on the value of the watermark information corresponding to the watermark index, performing a parity operation on the frequency value corresponding to the watermark index; The frequency value after the parity operation is performed and the original phase of the frequency value are used to perform an inverse short-time Fourier transform to obtain the trajectory data embedded with the watermark information.

2. The method according to claim 1, characterized in that Determining at least one frequency peak from the frequency values ​​corresponding to the sub-trace segments includes: Calculate the amplitude spectrum of each data in the time-frequency matrix data; The frequency value of the amplitude spectrum within a preset range is taken as the frequency peak value.

3. The method according to claim 1, characterized in that Before determining the timestamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index and calculating the watermark index of the timestamp, the method further includes: A random sequence is generated using a two-dimensional mapping method, and an XOR operation is performed on the random sequence and the image binary sequence to complete the encryption operation of the acquired copyright information.

4. The method according to claim 1, characterized in that The performing a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index comprises: When the value of the watermark information corresponding to the watermark index is 0, the frequency value corresponding to the watermark index is adjusted to an even number; When the value of the watermark information corresponding to the watermark index is 1, the frequency value corresponding to the watermark index is adjusted to an odd number.

5. The method according to claim 1, characterized in that The step of splitting the trajectory data acquired in real time according to the preset data extraction method to obtain at least one sub-trajectory segment includes: The data at the first preset position in the split current sub-track segment overlaps with part of the data in the previous sub-track segment; The data at the second preset position in the split current sub-track segment overlaps with part of the data in the next sub-track segment; The first preset position is before the second preset position.

6. The method according to claim 1, characterized in that The calculating the watermark index of the timestamp includes: Use the hash function to calculate the watermark index for the timestamp. The formula is as follows: ； is the time index, is the hash value of the time index, The watermark index is calculated based on the time index.

7. A device for embedding watermark information into real-time trajectory data, characterized in that: The device comprises: A splitting module, used to split the trajectory data acquired in real time according to a preset data extraction method to obtain at least one sub-trajectory segment; a conversion module, configured to convert the spatiotemporal trajectory data corresponding to the sub-trajectory segment into time-frequency matrix data according to the spatial attribute and the time attribute of the sub-trajectory segment, wherein the time-frequency matrix data includes a plurality of frequency values; A first determination module, configured to determine at least one frequency peak from the frequency values ​​corresponding to the sub-trace segments; A second determination module is used to determine a timestamp corresponding to the frequency peak value according to the corresponding relationship between the frequency peak value and the time index, and calculate a watermark index of the timestamp; an operation module, configured to perform a parity operation on a frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index; The transformation module is used to perform inverse short-time Fourier transformation using the frequency value after the parity operation and the original phase of the frequency value to obtain trajectory data embedded with watermark information.

8. The device according to claim 7, characterized in that The first determining module is specifically used for: Calculate the amplitude spectrum of each data in the time-frequency matrix data; The frequency value of the amplitude spectrum within a preset range is taken as the frequency peak value.

9. The device according to claim 7, characterized in that The device also includes: an encryption module, which is used to generate a random sequence by using a two-dimensional mapping method, and perform an XOR operation on the random sequence and the image binary sequence to complete the encryption operation of the acquired copyright information.

10. An electronic device, characterized in that: The electronic device includes a processor, a memory, and a program or instruction stored in the memory and executable on the processor, wherein the program or instruction is executed by the processor to perform the steps of the method for embedding watermark information into real-time trajectory data as described in any one of claims 1 to 6.

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